Cooking utensil having a graphite core

ABSTRACT

Provided is an article of cookware and a method of making the same. The cookware has a multi-layer bonded composite wall structure having an inner metal layer and an outer metal layer, and a core layer between the inner layer and the outer layer. The core layer has at least two perforated graphite plates, each plate having a plurality of spaced-apart holes formed therethrough, and at least one intermediate metal element disposed between the at least two perforated graphite plates and extending through the plurality of spaced-apart holes of each of the at least two perforated graphite plates. The at least one intermediate metal element is metallurgically bonded to the inner layer and the outer layer at least through the plurality of spaced-apart holes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority toU.S. patent application Ser. No. 14/797,489, filed Jul. 13, 2015 andentitled “Heat Zone Pan”, which is a continuation-in-part of and claimspriority to U.S. patent application Ser. No. 14/215,287, now issued asU.S. Pat. No. 9,078,539, filed Mar. 17, 2014 and entitled “Cookware WithSelectively Bonded Layers”, which in turn claims priority to U.S. PatentApplication No. 61/787,041, filed Mar. 15, 2013, all of which are herebyincorporated by reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to multi-ply, bonded cookware having acentral area of a cooking surface that has a higher level of thermalconductivity than a distal area of the cooking surface, as well assidewalls of the cookware. A method for making the cookware using solidstate bonding is also disclosed.

Description of Related Art

It has long been known to manufacture multi-layer bonded compositecookware in which various materials are joined together to combine thedesired physical properties of each of the materials into a composite.For example, the corrosion resistance of stainless steel is ideal forthe cooking surface as well as for the exterior surface of cookware;however, the thermal conductivity of stainless steel is not relativelyhigh. On the other hand, aluminum and/or copper offer much higherthermal conductivities and have been bonded to stainless steel toprovide well-known composite cookware items such as pots, pans, and thelike. Multi-layer bonded cookware is known in the art, as shown in anumber of patents, such as, for example: U.S. Pat. Nos. 4,246,045 and4,167,606 to Ulam; and U.S. Pat. Nos. 8,133,596 and 6,267,830 to Groll.These patents demonstrate that the manufacture of multi-layer bondedcookware comprising stainless steel outer layers bonded to centrallayer(s) of a higher conductivity aluminum and/or copper is well knownin the art. The bonding between layers of these different materials iscommonly achieved by conventional roll-bonding techniques using stripsof aluminum and/or copper, roll-bonded to outer strips of stainlesssteel. It is known that roll-bonding between copper, aluminum, andstainless steel layers is conventional in the art of making compositecookware.

A solid state bonding technique using high static pressure and heatapplied over time to make a plurality of composite blanks of, forexample, a combination of stainless steel-aluminum-stainless steel inthe manufactured cookware, is disclosed in U.S. Pat. No. 9,078,539 toGroll et al. There is a need in the art for producing cookware madeusing solid state bonding techniques for reducing the weight andimproving thermal characteristics of the cookware.

SUMMARY OF THE INVENTION

In view of the existing need in the art, it would be desirable todevelop new methods of producing cookware using solid state bondingtechniques. It would be further desirable to provide cookware made bysuch methods, wherein the cookware has reduced weight and improvedthermal characteristics over existing cookware made by solid statebonding techniques.

In accordance with one embodiment or aspect of the present disclosure,cookware may have a multi-layer bonded composite wall structure. Thecookware may have an inner metal layer and an outer metal layer, and acore layer between the inner layer and the outer layer. The core layermay have at least two perforated graphite plates, each plate having aplurality of spaced-apart holes formed therethrough, and at least oneintermediate metal element disposed between the at least two perforatedgraphite plates and extending through the plurality of spaced-apartholes of each of the at least two perforated graphite plates. The atleast one intermediate metal element may be metallurgically bonded tothe inner layer and the outer layer at least through the plurality ofspaced-apart holes.

In accordance with another embodiment or aspect of the presentdisclosure, cookware may have a multi-layer bonded composite wallstructure. The cookware may have an inner metal layer and an outer metallayer; and a core layer between the inner layer and the outer layer. Thecore layer may have at least two perforated graphite plates, each platehaving a plurality of spaced-apart holes formed therethrough, and atleast one metal core plate disposed between the at least two perforatedgraphite plates and extending through the plurality of spaced-apartholes of each of the at least two perforated graphite plates. The atleast one metal core plate may be metallurgically bonded to the innerlayer and the outer layer at least through the plurality of spaced-apartholes.

In accordance with another embodiment or aspect of the presentdisclosure, the at least one intermediate metal element may be analuminum plate. The at least one intermediate metal element can be adisc having a diameter equal to or larger than the at least twoperforated graphite plates. The at least one intermediate metal elementmay have a thickness of 0.032 in. At least one of the perforatedgraphite plates may have a thickness between 0.0010 in. and 0.0050 in.The inner layer may be stainless steel and have a thickness between0.010 in. to 0.015 in. The outer layer may be stainless steel and have athickness between 0.010 in. to 0.020 in. The inner layer and the outerlayer may be circular with a diameter of 5 in. to 25 in. The at leastone intermediate metal element may be a disc having a diameter of 5 in.to 25 in. At least one of the perforated graphite plates may be a dischaving a diameter of 2 in. to 20 in. At least one of the perforatedgraphite plates may be made from pyrolytic graphite. The plurality ofspaced-apart holes of at least one of the perforated graphite plates mayhave a diameter of 0.025 in. to 0.25 in. The at least one intermediatemetal element may be metallurgically bonded to the inner metal layer andthe outer metal layer in an area surrounding the at least two perforatedgraphite plates. The cookware may be formed as a fry pan. The cookwaremay have a bottom portion surrounded by a sidewall, and the at least twoperforated graphite plates may be located only in the bottom portion.The at least one metal core plate may have a pair of metal core platesdisposed between the at least two perforated graphite plates. The atleast two perforated graphite plates may have at least one perforatedgraphite plate disposed between the inner metal layer and the at leastone metal core plate, and at least one perforated graphite platedisposed between the metal core plate and the outer metal layer.

In accordance with another embodiment or aspect of the presentdisclosure, cookware may have an inner metal layer; an outer metallayer; and at least one perforated graphite plate having a plurality ofspaced-apart holes formed therethrough disposed between the inner metallayer and the outer metal layer. At least one of the inner metal layerand the outer metal layer may extend through the plurality ofspaced-apart holes of the at least one perforated graphite plate. Theinner metal layer may be metallurgically bonded to the outer metal layerat least through the plurality of spaced-apart holes.

In accordance with another embodiment or aspect of the presentdisclosure, at least one of the inner metal layer and the outer metallayer may be made as an aluminum plate. At least one of the inner metallayer and the outer metal layer may have a thickness of 0.032 in. Theperforated graphite plate may have a thickness between 0.0010 in. and0.0050 in. The inner layer may be stainless steel and have a thicknessbetween 0.010 in. to 0.015 in. The outer layer may be stainless steeland have a thickness between 0.010 in. to 0.020 in. The inner layer andthe outer layer may be circular with a diameter of 5 in. to 25 in. Theat least one perforated graphite plate may be a disc having a diameterof 2 in. to 20 in. The at least one perforated graphite plate may bemade from pyrolytic graphite. The plurality of spaced-apart holes of theat least one perforated graphite plate may have a diameter of 0.025 in.to 0.25 in. The inner metal layer may be metallurgically bonded to theouter metal layer in an area surrounding the at least one perforatedgraphite plate. The cookware may be formed as a fry pan. The cookwaremay have a bottom portion surrounded by a sidewall, and the at least oneperforated graphite plate may be located only in the bottom portion.

In accordance with another embodiment or aspect of the presentdisclosure, a method of making multi-layer bonded cookware may includeproviding an inner metal layer and an outer metal layer; providing acore layer between the inner layer and the outer layer to define astacked blank assembly, the core layer comprising at least twoperforated graphite plates, each plate having a plurality ofspaced-apart holes formed therethrough, and at least one metal coreplate disposed between the at least two perforated graphite plates; andapplying heat and pressure to the stacked blank assembly such that theat least one metal core plate is extruded through the plurality ofspaced-apart holes of each of the at least two perforated graphiteplates and is metallurgically bonded to the inner layer and the outerlayer at least through the plurality of spaced-apart holes.

In accordance with another embodiment or aspect of the presentdisclosure, a method of making multi-layer bonded cookware may includeproviding an inner metal layer and an outer metal layer; providing aperforated graphite plate between the inner metal layer and the outermetal layer to define a stacked blank assembly, the perforated graphiteplate having a plurality of spaced-apart holes formed therethrough; andapplying heat and pressure to the stacked blank assembly such that theinner metal layer is metallurgically bonded to the outer metal layer atleast through the plurality of spaced-apart holes of the perforatedgraphite plate.

These and other features and characteristics of the cookware describedherein, as well as methods of making such cookware, will become moreapparent upon consideration of the following description and theappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification, wherein like reference numeralsdesignate corresponding parts in the various figures. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration and description only.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is an exploded isometric view of a blank assembly of oneembodiment or aspect of the present disclosure;

FIG. 2 is a cross-sectional view of a bonded blank assembly of FIG. 1;

FIG. 3 is an enlarged view of Detail A shown in FIG. 2;

FIG. 4 is a cross-sectional view of a formed fry pan shape made from thebonded blank assembly of FIG. 2;

FIG. 5 is an exploded side view of a blank assembly of anotherembodiment or aspect of the present disclosure;

FIG. 6 is an exploded side view of a blank assembly of anotherembodiment or aspect of the present disclosure; and

FIG. 7 is an exploded side view of a blank assembly of anotherembodiment or aspect of the present disclosure.

In FIGS. 1-7, the same characters represent the same components unlessotherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the singular form of “a”, “an”, and “the” includesplural referents unless the context clearly dictates otherwise.

As used herein, spatial or directional terms, such as “left”, “right”,“up”, “down”, “inner”, “outer”, “above”, “below”, and the like, relateto various features as depicted in the drawing figures. However, it isto be understood that various alternative orientations can be assumedand, accordingly, such terms are not to be considered as limiting.

Unless otherwise indicated, all ranges or ratios disclosed herein are tobe understood to encompass any and all subranges or subratios subsumedtherein. For example, a stated range or ratio of “1 to 10” should beconsidered to include any and all subranges between (and inclusive of)the minimum value of 1 and the maximum value of 10; that is, allsubranges or subratios beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, such as but not limited to, 1to 6.1, 3.5 to 7.8, and 5.5 to 10.

As used herein, the term “substantially parallel” means a relative angleas between two objects (if extended to theoretical intersection), suchas elongated objects and including reference lines, that is from 0° to5°, or from 0° to 3°, or from 0° to 2°, or from 0° to 1°, or from 0° to0.5°, or from 0° to 0.25°, or from 0° to 0.1°, inclusive of the recitedvalues.

All documents, such as but not limited to issued patents and patentapplications, referred to herein, and unless otherwise indicated, are tobe considered to be “incorporated by reference” in their entirety.

As used herein, the term “solid state bonding” means a method of bondingtwo or more stacked plates of metals or metal alloys together using highpressure (typically over 5,000 psi) and high temperature (typically over600° F.), wherein the high pressure is applied in a normal or axialdirection, i.e., 90° relative to the plane of the stacked plates.

As used herein, the term “metallurgical bonding” or “metallurgicallybonded” refers to a bond formed between similar or dissimilar materialsthat is free of voids or discontinuities.

With reference now to the drawings, FIGS. 1-3 depict various views of ablank assembly 2 used in making one presently preferred embodiment ofthe cookware of the present invention. After appropriate surfacepreparation of the various layers of materials to be used in a bondingstep, the materials are positioned in an ordered array to create theblank assembly 2 as shown. In some examples, the surface preparationsteps may include degreasing, surface abrasion by chemical or mechanicalmethods, and the like.

The blank assembly 2 comprises upper and lower plates 4 and 8 which willform the inner and outer surfaces, respectively, of the cookware afterthe bonding and forming steps. In one exemplary and non-limitingembodiment, at least one of the upper and lower plates 4 and 8 is formedfrom metal, such as stainless steel, or titanium. In some examples, thestainless steel may be 300 grade or 400 grade stainless steel. Infurther examples, both the upper and lower plates 4 and 8 are formedfrom stainless steel. The upper and lower plates 4 and 8 may be discsabout 14 inches in diameter to form a near-net size blank for making afry pan of 10 inches in diameter. In other examples, the upper and lowerplates 4 and 8 may be discs from about 5 inches to about 20 inches indiameter. In this manner, scrap losses can be minimized. One of ordinaryskill in the art would readily appreciate that the size of the upper andlower plates 4 and 8 can be increased or decreased to make fry pans oflarger or smaller sizes, respectively. In some examples, the thicknessof upper and lower plates 4 and 8 may be about 0.015 to 0.03 inches. Thelower plate 8 of stainless steel may be made of a ferro-magneticstainless steel, such as a 400 grade in order to make the finishedcookware suitable for use on an induction cooking apparatus. The upperplate 4 is a food-grade stainless steel, such as an austenitic 300grade. In other examples, at least one of the upper and lower plates 4and 8 may be made from food-grade metal other than stainless steel, suchas titanium.

Between the upper and lower plates 4 and 8 is a central core layer 6.The central core layer 6 includes at least one perforated graphite plate10 having a plurality of spaced-apart holes 12 and at least oneintermediate metal element, such as at least one metal core plate 14.For example, as shown in FIGS. 1-3, the core layer 6 has a pair ofperforated graphite plates 10, with one plate positioned on each side ofa single metal core plate 14. After the solid state bonding process, themetal core plate 14 is extruded through the holes 12 of each perforatedgraphite plate 10 and is bonded with the upper and lower plates 4 and 8.In other examples, the core layer 6 has a pair of perforated graphiteplates 10 with two or more stacked metal core plates 14 positionedbetween the pair of perforated graphite plates 10. Preferably, oneperforated graphite plate 10 is directly between the upper plate 4 andthe metal core plate(s) 14, and the other perforated graphite plate 10is directly between the metal core plate(s) 14 and lower plate 8.

In some examples, the perforated graphite plate 10 is about0.0010-0.0050 inches thick and has the plurality of spaced-apart throughholes 12 formed therethrough. The size of the perforated graphite plate10 is sized to be smaller than the metal core plate 14 and the upper andlower plates 4 and 8 so that an outer edge of the perforated graphiteplate 10 is spaced radially inwardly from the outer edges of the metalcore plate 14, and the upper and lower plates 4 and 8. For example, adiameter of the perforated graphite plate 10 may be selected tocorrespond to a diameter of the cooking surface of the cookware 30 suchthat the perforated graphite plate 10 is spaced apart from the radiusedportion 32 of the formed cookware 30 (FIG. 4) in the region where a flatbottom 34 transitions to a sidewall 36. For a 10-inch fry pan, thediameter of the perforated graphite plate may be 7-9 inches, forexample.

The holes 12 in the perforated graphite plate 10 may be about 0.025-0.25inches in diameter. The holes 12 may be spaced apart from each otherrandomly, or in a pattern. For examples, the holes 12 may be arranged ina circular array. In various examples, the density of the holes 12(i.e., number of holes 12 per unit area) may be uniform across theperforated graphite plate 10, or it may vary between different portionsof the perforated graphite plate 10. For example, the density of theholes 12 may increase or decrease in a radial direction of theperforated graphite plate 10. In further examples, the holes 12 may beprovided in one or more groupings of holes 12.

The perforated graphite plate 10 may be made of pyrolytic graphite so asto transmit thermal energy primarily in a radial (rather than axial)direction. In this manner, the cooking surface can be heated uniformly,while avoiding hot spots. Graphite is preferably selected due to itshigh coefficient of thermal conductivity (approximately 1,700 W/mKversus approximately 200 W/mK for aluminum).

The metal core plate 14 of the central core layer 6 encapsulates theperforated graphite plate 10 between the upper and lower plates 4 and 8by being metallurgically bonded with the upper and lower plates 4 and 8during the solid state bonding process. In the example shown in FIGS.1-3, a bottom portion of the metal core plate 14 is extruded through theholes 12 of the lower perforated graphite plate 10 b during the solidstate bonding process and is bonded with the upper surface of the lowerplate 8. An upper portion of the metal core plate 14 is extruded throughthe holes 12 of the upper perforated graphite plate 10 a during thesolid state bonding process and is bonded with the lower surface of theupper plate 4. Because the metal core plate 14 is larger in diameterthan the perforated graphite plates 10 a, 10 b, the metal core plate 14is bonded with the upper and lower plates 4 and 8 over an entire surfaceof the metal core plate 14 surrounding the perforated graphite plates 10a, 10 b.

In one exemplary and non-limiting embodiment, the metal core plate 14 isformed from aluminum alloy, such as 1100 grade aluminum alloy. In otherexamples, the metal core plate 14 is formed from pure aluminum, aluminumclad metal, copper, or any other metal capable of metallurgicallybonding with the upper and lower plates 4 and 8. The metal core plate 14is larger than the perforated graphite plates 10 a, 10 b and may besized to correspond to the size of the upper and lower plates 4 and 8.For example, the metal core plate 14 may be a disc about 14 inches indiameter to form a near-net size blank for making a fry pan of 10 inchesin diameter. In other examples, the metal core plate 14 may be a discabout 2-20 inches in diameter. In this manner, scrap losses can beminimized. One of ordinary skill in the art would readily appreciatethat the size of the metal core plate 14 can be increased or decreasedto make fry pans of larger or smaller sizes, respectively. In someexamples, the thickness of the metal core plate may be about 0.032 to0.040 inches.

Having described the structure of the blank assembly 2 in accordancewith various embodiments or aspects of the present disclosure, a methodof making cookware using the blank assembly 2 will now be described.Initially, the blank assembly 2 is formed by stacking the central corelayer 6 on an upper surface of the lower plate 8. In the case of theblank assembly 2 shown in FIGS. 1-3, the central core layer 6 can bestacked on the lower plate 8 by placing the lower perforated graphiteplate 10 b on top of the lower plate 8, followed by the metal core plate14 and the upper perforated graphite plate 10 a. The upper plate 4 isthen stacked on a top surface of the upper perforated graphite plate 10a. Desirably, the upper plate 4, the central core layer 6, and the lowerplate 8 are aligned such that centers of each layer share a common axis.In some examples, the layers may be stacked such that their centers areoffset from one another. When stacked, the upper plate 4, the centralcore layer 6, and the lower plate 8 are substantially parallel to eachother.

The blank assembly 2, or a plurality of stacked blank assemblies 2, arethen placed in a press apparatus (not shown) for application of a loador pressure in the normal direction relative to the planes of plates inthe blank assemblies 2. While under a pressure of between 10,000 and20,000 psi, heat is applied to the blank assembly or assemblies 2between about 800° F. and 1,400° F. for a sufficient time (about 1-2hours) to achieve solid state bonding (i.e., metallurgical bonding)between the plates in the blank assembly or assemblies 2. During thesolid state bonding process, the material of the metal core plate 14 issoftened with the increase in temperature and is extruded through theholes 12 of the perforated graphite plates 10 a, 10 b to bemetallurgically bonded with the upper and lower plates 4 and 8. Goodbonding between stainless steel and aluminum is obtained at a pressureof 20,000 psi at a temperature of 860° F. after about one hour.

Each blank assembly 2 is then removed from the press apparatus andallowed to cool. In some examples, cooling may be accomplished byexposure to ambient air or by using a cooling agent, such as forced airor liquid.

After solid state bonding, the bonded blank assembly 2 is formed in adrawing press or hydroform machine (not shown) into a desired shape,such as a fry pan shape 30 depicted in FIG. 4. It will be seen in FIG. 4that the metal core layer 14 is extruded through the holes 12 in theperforated graphite plates 10 a, 10 b and is bonded to the upper andlower plates 4 and 8. The metal core layer 14 is further bonded to theupper and lower plates 4 and 8 in an area surrounding the perforatedgraphite plates 10 a, 10 b, such as in the area defining the sidewall 36of the fry pan 30. A handle or handles (not shown) may be attached tothe cookware in a known manner.

With reference to FIGS. 5-7, blank assemblies 2, useful in makingcookware, are shown in accordance with other preferred and non-limitingembodiments or aspects of the present disclosure. The components of theblank assemblies 2 shown in FIGS. 5-7 are substantially similar oridentical to the components of the blank assembly 2 described hereinwith reference to FIGS. 1-3. As the previous discussion regarding theblank assembly 2 generally shown in FIGS. 1-3 is applicable to theembodiments shown in FIGS. 5-7, only the relative differences betweenthe blank assembly 2 generally shown in FIGS. 1-3 and the blankassemblies shown in FIGS. 5-7 are discussed hereinafter.

With reference to FIG. 5, the blank assembly 2 comprises upper and lowerplates 4 and 8 which will form the inner and outer surfaces,respectively, of the cookware after the bonding and forming steps.Between the upper and lower plates 4 and 8 is a central core layer 6′.The central core layer 6′ includes three perforated graphite plates 10a, 10 b, and 10 c, and a pair of metal core plates 14 a, 14 b disposedbetween the perforated graphite plates 10 a, 10 b, and 10 c. Each of theperforated graphite plates 10 a, 10 b, 10 c has a plurality ofspaced-apart holes 12. After the solid state bonding process, the uppersurface of the upper metal core plate 14 a and the lower surface of thelower metal core plate 10 b are extruded through the holes 12 of thefirst and third perforated graphite plates 10 a, 10 c, respectively, andare metallurgically bonded with the upper and lower plates 4 and 8,respectively. The lower surface of the upper metal core plate 14 a andthe upper surface of the lower metal core plate 14 b are extrudedthrough the holes 12 of the intermediate perforated graphite plate 10 band are metallurgically bonded with each other. The upper and lowermetal core plates 14 are further bonded to the upper and lower plates 4and 8 in an area surrounding the perforated graphite plates 10 a, 10 b,and 10 c.

With reference to FIG. 6, the blank assembly 2 does not have a corelayer, such as the core layer 6 shown in FIGS. 1-3 or the core layer 6′shown in FIG. 5. Instead, the blank assembly 2 has an upper plate 4′made from a first material, such as stainless steel, and a lower plate8′ made from a second material, such as aluminum. The perforatedgraphite plate 10 having a plurality of holes 12, as described herein,is disposed between the upper and lower plates 4′ and 8′. In someexamples, a plurality of perforated graphite plates 10 may be stackedbetween the upper and lower plates 4′ and 8′. After the solid statebonding process, the upper surface of the lower plate 8′ is extrudedthrough the holes 12 of the perforated graphite plate(s) 10 and ismetallurgically bonded with the lower surface of the upper plate 4′. Theupper and lower plates 4′ and 8′ are further metallurgically bonded witheach other in an area surrounding the perforated graphite plate 10.

With reference to FIG. 7, the upper plate 4″, the lower plate 8″, andthe metal core plate 14″ are all made from the same material, such asaluminum. A pair of perforated graphite plates 10 a, 10 b, as describedherein, are disposed between the upper plate 4″, the lower plate 8″, andthe metal core plate 14″. In some examples, a plurality of perforatedgraphite plates 10 a may be stacked directly on one another between theupper plate 4″ and the metal core plate 14″, and/or a plurality ofgraphite plates 10 b may be stacked directly on one another between themetal core plate 14″ and the lower plate 8″. After the solid statebonding process, the lower surface of the upper plate 4″ and/or theupper surface of the metal core plate 14″ are extruded though the holesof the upper perforated graphite plate 10 a and are metallurgicallybonded together. At the same time, the upper surface of the lower plate8″ and/or the lower surface of the metal core plate 14″ are extrudedthrough the holes of the lower perforated graphite plate 10 b and aremetallurgically bonded together. The upper and lower plates 4″ and 8″are further metallurgically bonded with the metal core plate 14″ in anarea surrounding the perforated graphite plates 10 a, 10 b.

The solid state bonding technique of bonding pre-cut near net shapeplate blanks not only reduces scrap losses heretofore encountered in theconventional roll bonding manufacture of composite cookware but alsopermits the use of other materials in making multiple composites whichhave proven difficult, impossible and/or expensive to roll-bond. Forexample, solid state bonding permits the use of different grades ofstainless steel than otherwise possible in conventional roll bonding soas to lower costs of materials. Furthermore, solid state bonding furtherallows encapsulating of materials, such as graphite, that cannototherwise be bonded to stainless steel.

In various examples, the present invention may be further characterizedby one or more of the following clauses:

Clause 1. Cookware having a multi-layer bonded composite wall structure,the cookware comprising:

an inner metal layer and an outer metal layer; and

a core layer between the inner layer and the outer layer, the core layercomprising at least two perforated graphite plates, each of said atleast two perforated graphite plates having a plurality of spaced-apartholes formed therethrough, and at least one metal core plate disposedbetween the at least two perforated graphite plates and extendingthrough the plurality of spaced-apart holes of each of the at least twoperforated graphite plates,

wherein the at least one metal core plate is metallurgically bonded tothe inner layer and the outer layer at least through the plurality ofspaced-apart holes.

Clause 2. The cookware of clause 1, wherein the at least one metal coreplate is an aluminum plate.

Clause 3. The cookware of any of clauses 1-2, wherein the at least onemetal core plate has a thickness of 0.032 in.

Clause 4. The cookware of any of clauses 1-3, wherein at least one ofthe perforated graphite plates has a thickness between 0.0010 in. and0.0050 in.

Clause 5. The cookware of any of clauses 1-4, wherein the inner layer isstainless steel and has a thickness between 0.010 in. to 0.015 in.

Clause 6. The cookware of any of clauses 1-5, wherein the outer layer isstainless steel and has a thickness between 0.010 in. to 0.020 in.

Clause 7. The cookware of any of clauses 1-6, wherein the inner layerand the outer layer are circular with a diameter of 5 in. to 25 in.

Clause 8. The cookware of any of clauses 1-7, wherein the at least onemetal core plate has a diameter of 5 in. to 25 in.

Clause 9. The cookware of any of clauses 1-8, wherein at least one ofthe perforated graphite plates has a diameter of 2 in. to 20 in.

Clause 10. The cookware of any of clauses 1-9, wherein at least one ofthe perforated graphite plates is made from pyrolytic graphite.

Clause 11. The cookware of any of clauses 1-10, wherein the plurality ofspaced-apart holes of at least one of the perforated graphite plateshave a diameter of 0.025 in. to 0.25 in.

Clause 12. The cookware of any of clauses 1-11, wherein the at least onemetal core plate is metallurgically bonded to the inner layer and theouter layer in an area surrounding the at least two perforated graphiteplates.

Clause 13. The cookware of any of clauses 1-12, wherein the cookware isformed as a fry pan.

Clause 14. The cookware of any clauses 1-13, wherein the cookwarecomprises a bottom portion surrounded by a sidewall, and wherein the atleast two perforated graphite plates are located only in the bottomportion.

Clause 15. Cookware having a multi-layer bonded composite wallstructure, the cookware comprising: an inner metal layer; an outer metallayer; and at least one perforated graphite plate having a plurality ofspaced-apart holes formed therethrough disposed between the inner metallayer and the outer metal layer, at least one of the inner metal layerand the outer metal layer extending through the plurality ofspaced-apart holes of the at least one perforated graphite plate,wherein the inner metal layer is metallurgically bonded to the outermetal layer at least through the plurality of spaced-apart holes.

Clause 16. The cookware of clause 15, wherein at least one of the innermetal layer and the outer metal layer is made as an aluminum plate.

Clause 17. The cookware of clause 15 or clause 16, wherein at least oneof the inner metal layer and the outer metal layer has a thickness of0.032 in.

Clause 18. The cookware of one of clauses 15-17, wherein the at leastone perforated graphite plate has a thickness between 0.0010 in. and0.0050 in.

Clause 19. The cookware of one of clauses 15-18, wherein the inner layeris stainless steel and has a thickness between 0.010 in. to 0.015 in.

Clause 20. The cookware of one of clauses 15-19, wherein the outer layeris stainless steel and has a thickness between 0.010 in. to 0.020 in.

Clause 21. The cookware of one of clauses 15-20, wherein the inner layerand the outer layer are circular with a diameter of 5 in. to 25 in.

Clause 22. The cookware of one of clauses 15-21, wherein the at leastone perforated graphite plate has a diameter of 2 in. to 20 in.

Clause 23. The cookware of one of clauses 15-22, wherein the at leastone perforated graphite plate is made from pyrolytic graphite.

Clause 24. The cookware of one of clauses 15-23, wherein the pluralityof spaced-apart holes of the at least one perforated graphite plate havea diameter of 0.025 in. to 0.25 in.

Clause 25. The cookware of one of clauses 15-24, wherein the inner metallayer is metallurgically bonded to the outer metal layer in an areasurrounding the at least one perforated graphite plate.

Clause 26. The cookware of one of clauses 15-25, wherein the cookware isformed as a fry pan.

Clause 27. The cookware of one of clauses 15-26,wherein the cookwarecomprises a bottom portion surrounded by a sidewall, and wherein the atleast one perforated graphite plate is located only in the bottomportion.

Clause 28. A method of making multi-layer bonded cookware, the methodcomprising: providing an inner metal layer and an outer metal layer;providing a core layer between the inner layer and the outer layer todefine a stacked blank assembly, the core layer comprising at least twoperforated graphite plates, each plate having a plurality ofspaced-apart holes formed therethrough, and at least one metal coreplate disposed between the at least two perforated graphite plates; andapplying heat and pressure to the stacked blank assembly such that theat least one metal core plate is extruded through the plurality ofspaced-apart holes of each of the at least two perforated graphiteplates and is metallurgically bonded to the inner layer and the outerlayer at least through the plurality of spaced-apart holes.

Clause 29. A method of making multi-layer bonded cookware, the methodcomprising: providing an inner metal layer and an outer metal layer;providing a perforated graphite plate between the inner metal layer andthe outer metal layer to define a stacked blank assembly, the perforatedgraphite plate having a plurality of spaced-apart holes formedtherethrough; and applying heat and pressure to the stacked blankassembly such that the inner metal layer is metallurgically bonded tothe outer metal layer at least through the plurality of spaced-apartholes of the perforated graphite plate.

Clause 30. The cookware of any of clauses 1-14, wherein the at least onemetal core plate is a pair of metal core plates disposed between the atleast two perforated graphite plates.

Clause 31. The cookware of any of clauses 1-14 and 30, wherein the atleast two perforated graphite plates comprises at least one perforatedgraphite plate disposed between the inner metal layer and the at leastone metal core plate, and at least one perforated graphite platedisposed between the metal core plate and the outer metal layer.

The present invention has been described with reference to specificdetails of particular examples thereof. It is not intended that suchdetails be regarded as limitations upon the scope of the inventionexcept insofar as and to the extent that they are included in theaccompanying claims.

The invention claimed is:
 1. Cookware having a multi-layer bondedcomposite wall structure, the cookware comprising: an inner metal layerand an outer metal layer; and a core layer between the inner layer andthe outer layer, the core layer comprising at least two perforatedgraphite plates, each plate having a plurality of spaced-apart holesformed therethrough, and at least one intermediate metal elementdisposed between the at least two perforated graphite plates andextending through the plurality of spaced-apart holes of each of the atleast two perforated graphite plates, wherein the at least oneintermediate metal element is metallurgically bonded to the inner layerand the outer layer at least through the plurality of spaced-apartholes.
 2. The cookware of claim 1, wherein the at least one intermediatemetal element is an aluminum plate having a diameter equal to or largerthan a diameter of the at least two perforated graphite plates.
 3. Thecookware of claim 1, wherein the at least one intermediate metal elementhas a thickness of 0.032 in.
 4. The cookware of claim 1, wherein atleast one of the perforated graphite plate s has a thickness between0.0010 in. and 0.0050 in.
 5. The cookware of claim 1, wherein the innerlayer is stainless steel and has a thickness between 0.010 in. to 0.015in.
 6. The cookware of claim 1, wherein the outer layer is stainlesssteel and has a thickness between 0.010 in. to 0.020 in.
 7. The cookwareof claim 1, wherein the inner layer and the outer layer are circularwith a diameter of 5 in. to 25 in.
 8. The cookware of claim 2, whereinthe at least one intermediate metal element has a diameter of 5 in. to25 in.
 9. The cookware of claim 1, wherein at least one of theperforated graphite plate s has a diameter of 2 in. to 20 in.
 10. Thecookware of claim 1, wherein at least one of the perforated graphiteplates is made from pyrolytic graphite.
 11. The cookware of claim 1,wherein the plurality of spaced-apart holes of at least one of theperforated graphite plates have a diameter of 0.025 in. to 0.25 in. 12.The cookware of claim 1, wherein the at least one intermediate metalelement is metallurgically bonded to the inner metal layer and the outermetal layer in an area surrounding the at least two perforated graphiteplates.
 13. The cookware of claim 1, wherein the cookware is formed as afry pan.
 14. The cookware of claim 1, wherein the cookware comprises abottom portion surrounded by a sidewall, and wherein the at least twoperforated graphite plates are located only in the bottom portion.
 15. Amethod of making multi-layer bonded cookware, the method comprising:providing an inner metal layer and an outer metal layer; providing acore layer between the inner layer and the outer layer to define astacked blank assembly, the core layer comprising at least twoperforated graphite plates, each plate having a plurality ofspaced-apart holes formed therethrough, and at least one metal coreplate disposed between the at least two perforated graphite plates; andapplying heat and pressure to the stacked blank assembly such that theat least one metal core plate is extruded through the plurality ofspaced-apart holes of each of the at least two perforated graphite plates and is metallurgically bonded to the inner layer and the outer layerat least through the plurality of spaced-apart holes.
 16. The cookwareof claim 1, wherein at least one of the inner metal layer and outermetal layer is titanium.